Research on the Curving Aragonite Sheets in Clam’s Shell

Abstract:

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Molluscan shell possesses excellent strength, stiffness and fracture toughness that are
closely related to its exquisite microstructure. SEM observation of a clam’ shell showed that the
shell is a kind of bioceramic composite consisting of aragonite and protein layers parallel with the
surface of the shell. The observation also showed that the aragonite layers are composed of long and
thin aragonite sheets. Many aragonite sheets are of curving shape at the center of the shell. The
higher fracture toughness of the shell was analyzed based on the representative model of the
curving aragonite sheets and the concept of the maximum pullout force that is related to the fracture
toughness of the shell. The analytical result showed that the maximum pullout force of the curving
aragonite sheet is larger than that of straight aragonite sheets, which may effectively enhance the
fracture toughness of the shell.

Abstract: Molluscan shell is a typical biocomposite in nature. It possesses excellent strength,
stiffness and fracture toughness, which are closely related to its exquisite microstructure. SEM observation on clam’ shell shows that the shell is a kind of layered ceramic composite consisting of aragonite sheets and protein matrix. The aragonite sheets have long and thin shape and are arranged in a parallel manner. The higher fracture toughness of the shell is analyzed based on its representative model and the concept of maximal pullout energy. Analysis shows that the long and
thin shape as well as the parallel arrangement of these sheets will substantially improve the maximal pullout energy of the sheets and the fracture toughness of the shell.

Abstract: Molluscan shell is strong, stiff, tough and shows an erose fracture surface when it is
broken. In this research, the SEM observation on a Rufescens’s shell shows that the shell consists of
aragonite layers and collagen matrix. Each aragonite layer is parallel to the surface of the shell and
consists of many thin aragonite sheets. These aragonite sheets are perpendicular to the layer where
they are located. The observation also shows that the direction of the sheets in different layer is
various and a kind of herringbone distribution is found. The maximum pullout force of the
herringbone distribution is analyzed based on its representative model, and it shows that the
herringbone distribution can markedly increase the pullout force of the distribution and improve the
fracture toughness of the shell.

Abstract: The SEM observation on a conch’s shell shows that the shell is a kind of laminated bioceramic
composite composed of aragonite layers and organic matrix. Each aragonite layer is parallel with the
surface of the shell and consists of many thin aragonite sheets. These aragonite sheets are perpendicular to
the layer where they are located. The observation also shows that the orientations of the sheets in different
layers are different and these aragonite sheets compose various layups. A kind of lambdoidal layup is
found. The maximum pullout force of the lambdoidal layup is analyzed based on its representative model.
The result shows that the lambdoidal layup can markedly increase the pullout force of the layup and
improve the fracture toughness of the shell.

Abstract: A scanning electron microscope (SEM) was used for observing the microstructures of a
Mactridae shell. It showed that the shell is a kind of natural bioceramic composite, which consists of
aragonite sheets and organic matrix with laminated structure. It also showed that there are various
reinforced microstructures in the shell, which include a kind of lambdoidal one. The maximum
pullout force of the lambdoidal reinforced microstructure, which is related to the fracture toughness of
the shell, was analyzed and compared with that of a conventional 0°-structure based on their
representative models. The result indicated that the maximum pullout force of the lambdoidal
reinforced microstructure is markedly larger than that of the 0°-structure, which was experimentally
verified.

Abstract: Scanning electron microscope (SEM) observation shows that Solid-trough shell is a kind of bioceramic composite consisting of laminated aragonite and organic materials. The aragonite layers are parallel with the surface of the shell and consist of numerous thin and long aragonite fibers. The aragonite fibers in an arbitrary aragonite layers possess different directions and compose a kind of screwy microstructure. The maximum pullout force of the screwy microstructure was investigated and compared with that of parallel microstructure based on their representative models. It shows that the maximum pullout force of the screwy microstructure is markedly larger than that of the parallel microstructure, which was experimentally validated.